Objective: To determine the impact of maternal age on the rate of cesarean delivery in women undergoing induction at term.
Study design: Retrospective cohort study of term singleton gestations in nulliparous women induced for any indication at Lehigh Valley Health Network from July 2010 to July 2013. Exposure of interest was maternal age. Primary outcome was cesarean delivery. For every one woman ≥35 years of age (exposed), 2-3 women <35 years of age were selected as unexposed subjects for comparison. Statistical analysis included bivariate and multivariable techniques.
Results: 406 patients were included; 101 women ≥35 years of age and 305 women <35 years of age. Women in the ≥35 group were more likely to be induced for maternal medical conditions and less likely to be induced for prolonged pregnancy; few inductions were elective. Few women were induced electively in either group. More than half of women in both groups required cervical ripening. Method of cervical ripening and/or induction and percentage of women with a Bishop score <5 were similar between groups. The primary outcome, cesarean delivery, was similar between groups (45.5% in age ≥35 group vs 40.0% in age <35 group, p = .33). After adjustment for potential confounders, the rate of cesarean delivery was not influenced by maternal age (AOR 1.21 [0.76, 1.91], p = .42) but was higher in women with a Bishop score <5 at the time of induction of labor [AOR 1.64 [1.09, 2.47], p = .02].
Conclusion: In the wake of several recent trials underscoring the safety and potential maternal and fetal benefit of labor induction, identifying predictors of induction success (and failure) takes on increasing importance. Our findings suggest that maternal age is not an independent risk factor for cesarean delivery in women undergoing induction.
Keywords: Induction of labor; advanced maternal age; cesarean delivery; risk of cesarean delivery; term pregnancy.